This invention relates to a steering control apparatus for use in endless track type tractor and a valve of mono-spool type for use therewith.
A controlling gear for use in an endless track type tractor comprising two sets of steering members which enables steering, turning and braking of the tractor is described in Japanese Patent Publication No. 020,125/72.
A control valve for releasing a steering control clutch described in the Japanese Patent Publication No. 020,125/72 referred to above is installed on each of steering clutches on both sides of the tractor, and is of a type that, when either of two sets of steering clutch releasing control valves is selectively rendered operative, a fluid pressure releasing force is transmitted to the steering clutch to be actuated, while when the two steering clutch releasing control valves are operated individually or at the same time, they provide a control action such that transmission of the fluid pressure releasing forces to the steering clutches on both sides thereof is interrupted.
For this reason the steering control valve is disadvantageous in that it is complicated in construction and requires much labour and time for manufacture, and also the steering control system is complicated and tends to cause troubles.